Artillery rockets that are unguided are known to have large dispersion in flight, resulting in reduced military effectiveness. This dispersion is generally attributable to a launch-and-boost phase bias and random effects such as upper atmospheric or end game winds. The bias is compensated in some systems (generally referred to as "corrected launch rocket systems") by sensing the trajectory of the first launched rocket, comparing the actual trajectory with the desired trajectory and adjusting the launcher aiming for successive rounds. The trajectory sensing is normally implemented by radar tracking of a triggered beacon in the first rocket. Successive rockets need no beacon. One problem with the present approach is that high-power radiations from the tracking radar give away the location of the rocket artillery battery to the enemy. Further, there are the operational, logistic, and cost considerations associated with a radar transmitter. Another consideration is the jamming possibility introduced by requiring the radar to trigger the beacon through a receiver onboard the rocket. It is therefore concluded that an improvement to the tracking concept that eliminates the need for transmitting to the rocket and triggering a beacon in the rocket will be more operationally effective, less costly, and less vulnerable to electronic countermeasures and counterfire.
It is the objective of this invention to provide a technique of passive microwave three-dimensional tracking of a rocket with a high degree of accuracy, with low ECM vulnerability, with improved cost and general tactical utility.